The present invention relates to a device for steering a motor vehicle having two or more actuating parts.
DE 196 25 496 A1, discloses vehicle steering via actuating parts which themselves do not have any mechanical connection to the steered wheels. On such an actuating part, the driver predefines at least the desired value for the wheel steering angle for the steered wheels. Desired values for further actuating variables, such as vehicle speed and vehicle retardation, can also be predefined via the same actuating part. For example, two or more actuating parts are provided, via which the driver can predefine the desired value for the direction of travel. The actuating parts can be connected to one another mechanically or hydraulically.
For instance, EP 0 591 890 A1 discusses active actuating parts with force feedback in which haptic feedback is produced via actuating part control devices. A force which counteracts the deflection of the actuating part from its rest position is assigned via a characteristic map and is produced. For the purpose of coupling between the actuating parts, the same counteracting force can be produced on all the actuating parts. As a result, the impression of a coupling between the active actuating parts is produced.
Known mechanical or hydraulic coupling systems disadvantageously cannot be used in so-called active actuating parts having angle feedback. The known coupling of active actuating parts with force feedback in turn has the disadvantage that, when it is used in the motor vehicle, it is not ensured that the deflection of the actuating part from the rest position has a unique relationship to the actual transverse dynamic vehicle state (for example the steering angle produced on the steered wheels). For feeding back the steering angle of the wheels, this occurs when, as a result of mechanical influences (obstacles) on the wheels, the actuating members arranged at the wheel are not capable of adjusting the desired steering angle.
An object of the present invention is therefore, active actuating parts for steering a motor vehicle, to produce, on one hand a unique relationship between the wheel steering angles actually produced and to establish, on the other hand, the impression of a mechanical coupling of the actuating parts to one another.
This object has been achieved in accordance with the present invention by a device wherein the desired value for the transverse dynamic behavior (xcex4L,des) is determined from the forces acting on the actuating parts, and in that the current value (xcex4L,cur) of the transverse dynamic behavior produced by the actuating members is determined, a desired deflection (xcex4s,des) for the actuating parts being determined from the current value of the transverse dynamic behavior (xcex4L,cur), and each actuating part being assigned an actuating part control device by means of which the determined desired deflection (xcex4s,des) of the actuating part is adjusted.
The driver is able to predefine the desired vehicle transverse dynamics, for example the desired steering angle for the steered wheels, on at least two actuating parts. The desired value for the vehicle transverse dynamics is determined from the forces acting on the actuating parts. For this purpose, the mean value or the sum of the forces acting on the at least two actuating parts can, for example, be formed in a manner known per se, and this value can be assigned, via a characteristic map, a desired value for the vehicle transverse dynamics.
The desired value for the vehicle transverse dynamics is adjusted via the actuating members assigned to the steered wheels. The actual (current) value of the vehicle transverse dynamics which is produced by the actuating members, e.g., the wheel steering angle of steered wheels, is determined. The current transverse dynamic behavior is assigned a desired deflection of the actuating parts from the rest position, and the determined desired deflection of the actuating part is adjusted on each actuating part via an assigned actuating part control device.
The device according to the invention ensures that the driver obtains the impression that the actuating parts are connected to one another mechanically. The predefined relationship between the deflection of the actuating part and the actual vehicle transverse dynamics is always maintained.
According to another aspect of the invention, a desired steering angle is predefined via the actuating part, and the wheel steering angle is controlled in accordance with the predefinition of the desired steering angle via actuating members. The actuating part control device then controls the deflection of the actuating part on the basis of the wheel steering angle registered. Particularly advantageous aspects are the duration of the control cycles of the actuating part control device and actuating members being independent of one another. In order to achieve a jolt-free, continuous actuating part movement as sensed by the driver, it may be advantageous to operate on the actuating part control device with shorter control cycles than on the actuating members. In this case, it may additionally be advantageous to filter the determined current transverse dynamic behavior for the purposes of controlling the actuating part movement, in order that small control deviations do not lead to behavior of the actuating part which is unpleasant for the driver.